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Sanderthomas 12-02-2012 02:59 AM

1994 R100 GS electrical issues
Hi everybody. Hope this is in the right place. I'm not only new to working on motorcycles, but new to the sport as well. I don't think the ink is even dry on my motorcycle license. Anyway, here's my issue.
The brake light is only operating sporadically, as are the signals. The last time I took her out (and the first time I did so completely and totally legally), I noticed that if I turned the right signal on, I got a battery light coming on; there was no turn signal lit up. Ditto for the left side. The brake lights were working then. I just spent three hours futzing around with the wires, but I didn't really get anywhere. I thought I saw something on here about a simple relay replacement as a fix. Is that the way to go about it? I've got a Clymer manual and I do OK when working on our cars, but I'm not sure about the wiring. Any thoughts?

Clay Spinner 12-02-2012 04:09 AM

Anything electrical... I'd always start with making sure you have good grounds. After that start trouble shooting.

Mobiker 12-02-2012 07:48 AM


Originally Posted by Clay Spinner (Post 20160814)
Anything electrical... I'd always start with making sure you have good grounds. After that start trouble shooting.

Based on SanderThomas description, my first thought was also a bad ground(s).

I once got pulled over for no brakelights on an older car. I found 4 seperate shorts/ground problems. It apparantly took all 4 to blow the fuse. After I fixed them,no more problem. Point is it may be more than one small short/bad ground.

Beemerguru 12-02-2012 10:34 AM

Check both battery grounds, the main harness ground under the gas tank next to the voltage regulator..look for brown wire.

Also check the fuses under the left battery cover.

Battery light coming on when you turn something on (heated grips, turn signals, high beam, brake light) usually points to ground issues.

squish 12-02-2012 12:41 PM

Electrical systems can be daunting.

My first suggestion, pick up a book on motorcycle electrical systems, (Haynes makes a decent one)
And pick up a decent multimeter. and use the web to understand how to use it.
Use the book to understand the wiring diagram of your bike.

Then it's a really good idea to go over the whole system and clean every contact, switch and terminal.
I use dielectric grease on any contact that is solid, so no switches and I only use it on relays after they have been plugged in.

I use 1000+ grit sandpaper, pencil erasers and metal polish to clean connections. You want to remove the oxidization but not the plating of the terminal unless you have no other choice.

There are some products out there that are designed to clean up these connections, but I've not had good luck in these products getting the connections clean while not attacking paint, plastic or rubber. So I just do it by hand.
I've used alcohol on a q tip as a solvent, and canned air or an air compressor to clear things out.

If there are any connection that have gotten too hot, you need to understand why, and fix the problem.
You will see this as burnt, discolored or melted connections and or wires.

Corrosion = Resistance = Heat. Heat increases the speed of corrosion, and the cycle gets worse and worse.

Relays go bad, or more likely there's enough resistance in the wiring and plugs that they get garfed up.

I've found that new relays have solved a lot of the really weird or random light, horn, turn signals issues I've had.

One thing to remember, BMW likes to do things their own way and they love their special (and expensive relays)
So it's best to make sure everything else in the system is clean and solid and good connections before going in and replacing relays.

Good luck.

bmwblake 12-02-2012 01:33 PM

it's not a bad idea to check the health of your battery as well. your situation sounds like a ground issue but before you start troubleshooting i'd make sure the battery is healthy. make sure you test it under a load as well as static voltage.

Sanderthomas 12-02-2012 07:23 PM

New to do list
Wow. Thanks everyone for the advice! Looks like I'll be puttering in the garage for a while. I'll keep you posted!

Uncle Pollo 12-03-2012 06:56 AM

There is a wire coming from a switch n the brake lever assembly. Wiggle it aa bit while pulling the brake lever. Mine failed after 26 years. I soldered it.

Sanderthomas 12-03-2012 12:03 PM

Okay, now the horn isn't working. Looking at possible replacement of relays from local auto parts store. Is a close analog available that will work? Looking to avoid spending too much for now. I haven't had time yet to look more closely at the wires and everything. I am guessing I will need to remove the tape wrapping everything. Also, I think one of the small black relays is what I want to replace. Am I right? Or is it the big red unit in front of the relay section?

Clay Spinner 12-03-2012 12:41 PM

So you've cleaned all of the ground wire attachments... and now the only thing not working is the horn... I'm unclear what has changed since your first post.

Sanderthomas 12-03-2012 04:07 PM

Sorry for the confusion... I'm new

Originally Posted by Clay Spinner (Post 20169856)
So you've cleaned all of the ground wire attachments... and now the only thing not working is the horn... I'm unclear what has changed since your first post.

Clay Spinner- Apologies. After re-reading my last post, I see I made it as clear as mud. What I meant to say was that the horn, along with the brake and signal lights, is not working. However, (and try not to laugh at my incompetence) I now believe that the reason was because I had unknowingly disconnected the flasher relay, which seems to also control the horn. I haven't gone through and cleaned all the connectors, but I definitely would like to avoid paying $115 for a new OEM flasher relay. Anyway, I'll hopefully get into the wiring soon. Any suggestions for removing the fabric tape that binds all of the wires/harnesses together?

squish 12-03-2012 10:36 PM

I replaced the two smaller black relays with four pole relays and they are working fine but I went over the wiring diagram and made sure that it would. Autozone and napa might carry the five pole relay iirc it's also common to Audi and is used both for a fuel pum and a window regulator but I don't know the number.

On my bike one was a load shed relay the other worked with the headlight blinkers and horn. I replaced them both and they went south on me again after about 1k miles that's when I went with the four pole and have had no issues since.

But before spending the money on relays make sure the wiring is in good shape. Before digging the harness open look to see if there is any thing indicating a problem. Like over heated connections. A short buried in the harness will often show itself at the plugs.

Sanderthomas 12-22-2012 10:12 PM

Well, I went through and cleaned a bunch of grounds, disassembled and reassembled the switches on the handles, and it seemed to fix the issue. However, a fuse blew while I was putting the bike back together. This was the rearmost fuse. It had seemed a bit titchy as I was putting her back together, in that it seemed to have a poor connection. If I wiggled it the lights would go off (opening the circuit). I replaced the blown fuse. Also the big blacker lay marked "blinkerelais" first buzzed when I was attempting to use the right turn signal, with no accompanying lights. To Make a long story short, I now have brake lights when the ignition switch is in the on position, as well as turn signals. No tail light though. Man trying to type on an iPod Touch is difficult. I haven't tried the horn yet. I did take her out the next day though. I rode in traffic in my little town a whole two miles. To buy diapers. Now I have to be sure the ground for the fuse box is OK. Have to wait til after Christmas though, as I have a a smaller bike to assemble for my oldest son. Thanks everyone for the advice. I'll keep you posted.

Sanderthomas 02-14-2013 04:01 AM

Thanks Everyone
By following your sage advice, I got things going right. I spent a very late night cleaning contacts and she's got her signals,tail, and brake lights working now. I took her out for my first real ride not long after- 65 miles. It was a lot of fun.

homere 02-14-2013 09:25 PM

gs electrics
I have a1993 r100gs. Had a the right side blinkers came on when the engine was running.Would not turn off.They worked perfectly when the engine was off, I changed the plug wires and now it works perfect.

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